Conventional heart-rate belts and heart rate bands typically comprise a body made of plastic, on the surface of which there are two local electrodes to be placed against the chest. Electronics for transmitting a heart rate signal, typically to a wrist-band device, are built into the plastic body. Conductors from the electrodes to the electronics also run inside the body, which is generally attached against the chest with the aid of a flexible band.
Because plastic heart rate bands are relatively thick and can feel uncomfortable in use, heart rate belts and sensors utilizing textile materials have recently been developed. However some of these developments have the disadvantage of unreliable contacts, electrical insulation, and interference of electrical signals. These disadvantages with the prior art are discussed in US Patent Application Publication No. 2007/0285868 (Lindberg et al).
The sensor arrangement disclosed in US Patent Application Publication No. 2007/0285868 overcomes some of the problems with the prior art by ensuring that the transmission conductor that interconnects the electrode with the electronics module is well insulated. In this prior art the sensor is made from a number of layers, two of which are insulation layers. One of these insulation layers has the task of preventing liquid, for example perspiration from reaching the transmission conductor layer and thereby preventing electrical interference. However, this sensor arrangement of multiple layers is laborious and costly to make.
The object of the present invention is to provide a sensor that overcomes or substantially ameliorates at least one of the problems associated with the prior art.